JP2021125816A - Moire suppression method, moire suppression device, and moire suppression system - Google Patents

Abstract

To provide means for more effectively suppressing the occurrence of moire by breaking a halftone dot cycle.SOLUTION: A moire suppression method includes the steps of generating a grid that divides each halftone dot into individual cells for a first region where moire occurs in an input image represented by the halftone dot, and moving at least a part of the halftone dot of the ratio determined on the basis of a first arbitrary value in the halftone included in the grid according to the movement amount determined on the basis of a third arbitrary value and a movement direction determined on the basis of a second arbitrary value. At least one of the first arbitrary value, the second arbitrary value, and the third arbitrary value is a pseudo-random number.SELECTED DRAWING: Figure 2

Description

The present invention relates to a moire suppressing method, a moire suppressing device, and a moire suppressing system.

"Moire (or moire)" is an interference fringe that is visually generated when a plurality of periodic patterns and structures are superposed. Also, physically speaking, moire can be said to be a beat phenomenon of two spatial frequencies.
Although this moiré may be actively used as a useful one, if unintended moiré occurs, the design of the image may be impaired and the quality of printed matter may deteriorate. Means have also been proposed.

For example, in Patent Document 1, as a means for reducing the strength of moire generated in a digital binary image, "moire is generated in a digital image including halftone dots read from a scanner or a digital image that has been enlarged / reduced. Is detected in units of one halftone dot to reduce the occurrence of moire as follows. As shown in FIG. 1A, each cell is point-symmetric with respect to the center of each detected cell. The shape is corrected so that the shape is close to, and as shown in FIG. 1 (b), the cells are moved so that the position coordinates of the centers of at least nine adjacent cells are statistically even. Further, as shown in FIG. 1 (c), the distance between the detected reference cell and at least four or more cells adjacent to the reference cell is equal. The technique of "correcting the shape of the reference cell so as to be" is described.

Japanese Unexamined Patent Publication No. 2001-346038

In the image processing system of Patent Document 1, when halftone dots in a cell of interest exist at positions where the distances from adjacent cells are uneven and moire occurs due to the cycle, the halftone dots are statistically even. By moving the halftone dots in the cell of interest or correcting the shape of the halftone dots, the period of the halftone dots is disrupted and moire is suppressed.

However, in the image processing system of Patent Document 1, for example, when halftone dots express the contour of image data and the halftone dots in the contour region and the screen angle interfere with each other to cause moire, attention is paid to the case. Even if the halftone dots in a cell are statistically moved according to the halftone dots of adjacent cells, it is assumed that the period of the halftone dots cannot be completely broken and the moire suppression effect is weakened.
Therefore, there is a need for a means for suppressing moire more effectively.

Therefore, the present invention has been made in view of such a problem, and an object of the present invention is to provide a means for more effectively suppressing the occurrence of moire by breaking the period of halftone dots.

In order to solve the above problems, one of the typical moire suppressing methods of the present invention is to use each halftone dot for the first region where moire is generated in the input image represented by halftone dots. The process of generating a grid that divides points into individual cells and the ratio of halftone dots included in the grid determined based on the first arbitrary value are determined based on the second arbitrary value. Of the first arbitrary value, the second arbitrary value, and the third arbitrary value, including the step of moving according to the movement direction determined and the movement amount determined based on the third arbitrary value. At least one of them is a pseudo-random number.

According to the present invention, it is possible to provide a means for more effectively suppressing the occurrence of moire by breaking the period of halftone dots.

FIG. 1 is a diagram showing a computer system for carrying out an embodiment of the present invention. FIG. 2 is a diagram showing an example of a configuration of a moire suppression system according to an embodiment of the present invention. FIG. 3 is a diagram showing an example of moire. FIG. 4 is a diagram showing another example of moiré. FIG. 5 is a diagram for explaining halftone dots according to the embodiment of the present invention. FIG. 6 is a diagram for explaining the screen angle of halftone dots. FIG. 7 is a diagram for explaining the screen angle of halftone dots. FIG. 8 is a diagram showing an outline of a printing machine. FIG. 9 is a diagram showing an outline of the internal configuration of the ink coating unit of the printing machine. FIG. 10 is a diagram for explaining a printing plate. FIG. 11 is a diagram for explaining a printing plate. FIG. 12 is a diagram for explaining a printing plate. FIG. 13 is a diagram for explaining a printing plate. FIG. 14 is a diagram for explaining an example of the movement of halftone dots according to the embodiment of the present invention. FIG. 15 is a diagram for explaining an example of the movement of halftone dots according to the embodiment of the present invention. FIG. 16 is a flowchart showing a moire suppressing method according to an embodiment of the present invention. FIG. 17 is a diagram showing a flow of processing for extracting a contour region according to an embodiment of the present invention. FIG. 18 is a diagram showing a flow of processing for extracting a contour region according to an embodiment of the present invention. FIG. 19 is a diagram showing a specific example in the case where contour extraction is performed by the procedure shown in FIGS. 17 to 18. FIG. 20 is a diagram showing a specific example in the case where contour extraction is performed by the procedure shown in FIGS. 17 to 18. FIG. 21 is a diagram showing a result of extracting a contour region from the print image data after the smoothing process and before the halftone dot formation and the print image data shown in FIG. 20. FIG. 22 is a diagram showing an example of a contour image extracted by binarizing the image shown in FIG. 21. FIG. 23 is a diagram showing overlapping images in which the contour images shown in FIG. 22 are superimposed and displayed. FIG. 24 is a diagram showing a configuration of a grid according to an embodiment of the present invention. FIG. 25 is a diagram for explaining the movement ratio of halftone dots according to the embodiment of the present invention. FIG. 26 is a diagram for explaining a moving direction of halftone dots according to an embodiment of the present invention. FIG. 27 is a diagram for explaining the amount of movement of halftone dots according to the embodiment of the present invention. FIG. 28 is a diagram for explaining the amount of movement of halftone dots according to the embodiment of the present invention. FIG. 29 is a diagram for explaining a process when the halftone dots according to the embodiment of the present invention move and cross the cell boundary line.

As described above, moire is a phenomenon in which when patterns having different cycles are overlapped, a new pattern not included in each pattern is generated. For example, it is assumed that a periodic pattern such as a striped pattern exists in the image data for printing at the time of submission in commercial printing. When this pattern is represented by halftone dots, the period of the pattern and the period of the halftone dots interfere with each other, and a new pattern that does not exist in the original image data may appear as moire. An example of moiré is shown in FIGS. 3 to 4 described later. Further, as shown in FIGS. 3 to 4, a halftone dot is a minimum unit for expressing the gradation of a drawing target by a plurality of dots (that is, pixels).

In the field of commercial printing, a method is adopted in which an image data for printing at the time of submission is input and an image is expressed by monochrome binary halftone dots for each print element color by RIP (Raster Image Processor) processing. .. RIP processing refers to rasterizing digital data created by a general-purpose computer into a data format that can be output by a printing machine, and the drawing data is represented by halftone dots of a certain size.

Generally, in the expression of color using halftone dots, it is expressed by subtractive color mixing by four colors (this is called R4C) of C (cyan), M (magenta), Y (yellow), and K (ink). Then, for each of the C, M, Y, and K colors, a plate for expressing the drawing contents by printing is prepared, and the shading information and the colors are reproduced by overlaying ink on the paper.

In creating the data to be drawn for each version described above, a color conversion called a profile is used to match the color space of the original data (for example, RGB color system) with the color space of the printing machine (CMYK color system). Select any table and perform color matching. The profile is configured in a look-up table (LUT) format, and is created by dividing the RGB space, the CMYK space, or the L * a * b space for each component and determining a representative value. Then, at the time of the color matching process, the input image data is approximated to the representative value, and the corresponding output value is calculated by referring to the lookup table.

AM screening (Amplitude Modulation Screening) that changes the size of halftone dots and FM screening that keeps the size of halftone dots constant and changes the density are typical methods of gradation expression (shading expression) using halftone dots. (Frequency Modulation Screening). In FM screening, since the arrangement of halftone dots is irregular, moire does not occur in principle, but it is technical to reproduce minute points perfectly without positional deviation or dot gain (spread of halftone dots). Difficult to. AM screening is resistant to plate misalignment and has a low technical difficulty level, so it is generally used in commercial printing where mass production is essential while stabilizing quality.

In order to reproduce colors, in AM screening, instead of overlapping halftone dots at the same position and mixing ink, the illusion of the eyes (this is called an optical illusion) is used to see the set of dots from a distance. Sometimes it looks like any pattern or color. Further, the halftone dots of each color have an arbitrary angle (this is called a screen angle) as shown in FIG. 6, and the distance between the centers of the halftone dots is arranged to be constant (hereinafter, the halftone dot generation interval and the like). I will call it). In this way, if a certain period and angle are given, halftone dots of each color interfere with each other, and moire occurs.

Moire is strongly visible when the difference in screen angle between versions is small. Generally, in four-color printing, each color is provided with a screen angle as shown in FIG. 7 so that moire is not noticeable. However, moire that occurs in the field of commercial printing is not only due to interference between halftone dots, but also on the period of the input image data for printing and the data output after halftone dot processing is performed on the data. However, there are some that occur due to the interference of halftone dot periods.

In the field of commercial printing, when a printed matter is visually inspected and it is confirmed that moiré has occurred, in order to suppress moiré, the original image data before halftone dot processing by RIP processing is returned and moire is removed. Make corrections to suppress. The data is modified by the operator. After that, halftone dot data for printing is created again by RIP processing, and the printed matter is visually inspected again.

However, it is troublesome and costly to print each time a correction is made and to carry out a visual inspection. In addition, although visual evaluation is performed with great effort and cost, it is difficult to completely prevent accidents such as printing stoppage and reprinting. Therefore, there is a demand for a means of suppressing moire by processing / correcting halftone dot data instead of returning to the original image data and making corrections.

Further, as described above, there are known means for alleviating moiré by uniformly moving the halftone dots constituting the RIP-processed image all at once and correcting the shape. Moire cannot be completely suppressed because the period of the halftone dots is not completely broken by the means for correcting the halftone dots all at once and evenly.

Therefore, the present inventor has come up with the idea that the halftone dot period can be more effectively disrupted by moving the halftone dots based on pseudo-random numbers. However, if the halftone dots are moved based on the pseudo-random numbers, noise may be generated and the outline portion that defines the structure of the object in the image may be blurred. Therefore, the present inventor does not modify the halftone dots all at once, but moves only the halftone dots in the region where the moire occurs in the image excluding the contour portion based on the pseudo-random number, thereby producing the moire effect. We succeeded in obtaining a clearer image that suppresses noise and maintains the structure of the object.

From the above, according to the present invention, it is possible to provide a moire suppressing means for suppressing deterioration of the quality of printed matter by suppressing the generation of noise due to the movement of halftone dots without changing the color of the printed matter. Become. In other words, since the structure of the halftone dots that cause moire in the printed matter is broken, it is possible to obtain an image in which the appearance of moire is not visually recognized regardless of the direction in which the printed matter is confirmed.

Hereinafter, the background on which the present invention is premised and the embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to this embodiment. Further, in the description of the drawings, the same parts are indicated by the same reference numerals.
(Hardware configuration)

First, with reference to FIG. 1, a computer system 300 for carrying out the embodiment of the present disclosure will be described. The mechanisms and devices of the various embodiments disclosed herein may be applied to any suitable computing system. The main components of the computer system 300 include one or more processors 302, memory 304, terminal interface 312, storage interface 314, I / O (input / output) device interface 316, and network interface 318. These components may be interconnected via memory bus 306, I / O bus 308, bus interface unit 309, and I / O bus interface unit 310.

The computer system 300 may include one or more general purpose programmable central processing units (CPUs) 302A and 302B collectively referred to as processors 302. In one embodiment, the computer system 300 may include a plurality of processors, and in another embodiment, the computer system 300 may be a single CPU system. Each processor 302 may execute an instruction stored in memory 304 and include an onboard cache.

In certain embodiments, the memory 304 may include a random access semiconductor memory, a storage device, or a storage medium (either volatile or non-volatile) for storing data and programs. The memory 304 may store all or part of the programs, modules, and data structures that perform the functions described herein. For example, the memory 304 may store the moire suppression application 350. In certain embodiments, the moire suppression application 350 may include instructions or descriptions that perform functions described below on the processor 302.

In certain embodiments, the moire suppression application 350 is a semiconductor device, chip, logic gate, circuit, circuit card, and / or other physical hardware device instead of or in addition to a processor-based system. It may be implemented in hardware via. In certain embodiments, the moire suppression application 350 may include data other than instructions or descriptions. In certain embodiments, a camera, sensor, or other data input device (not shown) may be provided to communicate directly with the bus interface unit 309, processor 302, or other hardware of the computer system 300. ..

The computer system 300 may include a processor 302, a memory 304, a display system 324, and a bus interface unit 309 that communicates between the I / O bus interface unit 310. The I / O bus interface unit 310 may be connected to an I / O bus 308 for transferring data to and from various I / O units. The I / O bus interface unit 310, via the I / O bus 308, is a plurality of I / O interface units 312, 314, 316, also known as I / O processors (IOPs) or I / O adapters (IOAs). And 318 may be communicated.

The display system 324 may include a display controller, display memory, or both. The display controller can provide video, audio, or both data to the display device 326. The computer system 300 may also include devices such as one or more sensors configured to collect the data and provide the data to the processor 302.

For example, the computer system 300 includes a biometric sensor that collects heart rate data, stress level data, etc., an environment sensor that collects humidity data, temperature data, pressure data, etc., and a motion sensor that collects acceleration data, exercise data, etc. May include. Other types of sensors can also be used. The display system 324 may be connected to a stand-alone display screen, a display device 326 such as a television, tablet, or portable device.

The I / O interface unit has a function of communicating with various storages or I / O devices. For example, the terminal interface unit 312 may be a user output device such as a video display device or a speaker TV, or a user input device such as a keyboard, mouse, keypad, touchpad, trackball, button, light pen, or other pointing device. Such a user I / O device 320 can be attached. The user inputs input data and instructions to the user I / O device 320 and the computer system 300 by operating the user input device using the user interface, and receives the output data from the computer system 300. May be good. The user interface may be displayed on the display device via the user I / O device 320, reproduced by the speaker, or printed via the printer, for example.

The storage interface 314 is an array of disk drives or other storage device configured to appear as a single disk drive, although one or more disk drives or direct access storage device 322 (usually a magnetic disk drive storage device). It may be). In certain embodiments, the storage device 322 may be implemented as any secondary storage device. The contents of the memory 304 are stored in the storage device 322 and may be read out from the storage device 322 as needed. The I / O device interface 316 may provide an interface to other I / O devices such as printers and fax machines. The network interface 318 may provide a communication path so that the computer system 300 and other devices can communicate with each other. This communication path may be, for example, network 330.

In certain embodiments, the computer system 300 is a device that receives a request from another computer system (client) that does not have a direct user interface, such as a multi-user mainframe computer system, a single user system, or a server computer. There may be. In other embodiments, the computer system 300 may be a desktop computer, a portable computer, a laptop computer, a tablet computer, a pocket computer, a telephone, a smartphone, or any other suitable electronic device.

Next, the configuration of the moire suppression system according to the embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a diagram showing an example of the configuration of the moire suppression system 360 according to the embodiment of the present invention. As shown in FIG. 2, the moire suppression system 360 mainly includes a client terminal 365, a communication network 370, a printing unit 375, and a moire suppression device 380. The client terminal 365, the printing unit 375, and the moire suppression device 380 are connected to each other via the communication network 370.
The communication network 370 may include, for example, a local area network (LAN), a wide area network (WAN), a satellite network, a cable network, a WiFi network, or any combination thereof. Further, the connection of the client terminal 365, the printing unit 375, and the moire suppression device may be wired or wireless.

The client terminal 365 is a terminal that transmits input data to be processed by the moire suppression method described later to the moire suppression device via the communication network 370. The client terminal 365 may be a terminal used by an individual or a shared terminal in an organization such as a private company. Further, the client terminal 365 may be any device such as a desktop personal computer, a notebook personal computer, a tablet, or a smartphone.

The data storage unit 372 stores image data (hereinafter, “input data”) represented by halftone dots, which is a target of the moire suppression method, transmitted from the client terminal 365 via the communication network 370. It is the storage part of. This data storage unit may be, for example, a local storage such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive), or may be a cloud-type storage area accessible to the moire suppression device 380.

The halftone dot generation condition input unit 374 is a functional unit for inputting halftone dot generation conditions for the input data stored in the data storage unit 372. These halftone dot generation conditions include, for example, the number of screen lines, the screen angle, and the like. Further, the halftone dot generation condition input unit may be a user I / O interface capable of receiving input from the user, such as a touch screen, a mouse, a keyboard, and a voice recognition device.

The moire suppressing device 380 is a device for carrying out the processing in the moire suppressing method according to the embodiment of the present invention. The moire suppression device 380 inputs the input data stored in the data storage unit 372 and the halftone dot generation condition input via the halftone dot generation condition input unit 374.

Further, as shown in FIG. 2, the moire suppression device 380 has a halftone dot region extraction unit 382, a halftone dot movement condition determination unit 384, and a halftone dot movement process in order to carry out the moire suppression method according to the embodiment of the present invention. A unit 386, an exception handling unit 388, and an image output unit 390 are included.

The halftone dot area extraction unit 382 sets a grid area in which each halftone dot of the input data input from the data storage unit 372 is accommodated based on the halftone dot generation condition input via the halftone dot generation condition input unit 374. It is a functional part that extracts the halftone dot area by forming it.

The halftone dot movement condition determination unit 384 sets the movement conditions such as the movement ratio, the movement direction, and the movement amount of the halftone dots in the halftone dot area extracted by the halftone dot area extraction unit 382 as pseudo-random numbers. It is a functional part that is determined based on.

The halftone dot movement processing unit 386 is the target grid extracted by the halftone dot area extraction unit 382 in the input data input from the data storage unit 372 based on the movement condition determined by the halftone dot movement condition determination unit 384. It is a functional part that moves the halftone dots included in the area.

The exception handling unit 388 is a functional unit that performs exception handling described later when at least a part of the halftone dots crosses the boundary line of the cells of the grid as a result of the halftone dot movement processing unit 386 moving the halftone dots. ..

Further, the image output unit 390 is a functional unit that outputs image data after moire is suppressed by the processing of the functional unit of the halftone dot region extraction unit 382 to the exception processing unit 388.

The printing unit 375 is a printing unit for printing the image data represented by the halftone dots after the moire is suppressed, which is generated by the moire suppressing device 380.
The printing unit 375 may print an image output from the image output unit 390 of the moire suppression device 380, and after the image output from the image output unit 390 is returned to the client terminal 365, the client terminal Printing may be performed according to the request of 365.

Each functional unit included in the moire suppression system 360 may be a software module constituting the moire suppression application 350 shown in FIG. 1, or may be an independent dedicated hardware device. Further, the above-mentioned functional unit may be implemented in the same computing environment, or may be implemented in a distributed computing environment. For example, the halftone dot generation condition input unit 374 may be mounted on a remote server or client terminal 365, and other functional units may be mounted on the moire suppression device 380.

Further, the embodiment of the present invention is not limited to the configuration of the moire suppression system 360 described with reference to FIG. For example, any configuration is possible, such as a configuration in which the moire suppression device 380 is directly connected to the client terminal 365, a configuration in which the moire suppression device 380 and the client terminal 365 are integrated, and the like.

Next, an example of moire will be described with reference to FIGS. 3 to 4.

FIG. 3 is a diagram showing an example in which moire occurs. In FIG. 3, four patterns 21, 22, 23, and 24 represented by halftone dots are shown. The halftone dots of these patterns 21, 22, 23, and 24 are arranged at the same interval, but since the slopes of each are different, the period of the halftone dots is also different. Further, the pattern 25 is a stack of patterns 21, 22, 23, and 24 centered on each other. As shown in FIG. 3, a circular pattern or a straight line pattern, which did not exist in any of the patterns 21, 22, 23, and 24 before overlapping, is generated in the pattern 25 as moire.

FIG. 4 is a diagram showing another example of moiré. In FIG. 4, a pattern 26 in which halftone dots are regularly arranged and a pattern 27 in which lines are regularly arranged are shown. Further, the pattern 28 is a stack of the pattern 26 and the pattern 27. As shown in FIG. 4, a pattern of regular straight lines in the diagonal direction, which did not exist in either the pattern 26 or the pattern 27, is generated in the pattern 28 as moire.

Next, the halftone dots according to the embodiment of the present invention will be described with reference to FIG.

FIG. 5 is a diagram for explaining halftone dots according to the embodiment of the present invention. FIG. 5 shows a gradation pattern 31 in which the brightness changes smoothly, and enlarged regions 32, 33, and 34 in which a part of the gradation pattern 31 is extracted and enlarged. As shown by the enlarged regions 32, 33, and 34, the density of the gradation pattern 31 is appropriately expressed by varying the size of halftone dots (dots) having a size that cannot be seen with the naked eye. be able to.

Next, the screen angle of the halftone dots will be described with reference to FIGS. 6 to 7.

FIG. 6 is a diagram for explaining the screen angle of halftone dots. FIG. 6 shows a slope pattern 36 in which halftone dots are arranged and sloped.

As mentioned above, in AM screening, in order to reproduce colors, dots are used by using an optical illusion (this is called an "optical illusion") instead of overlapping halftone dots at the same position and mixing ink. When viewed from a distance, the set of ink is shown in any pattern or color.
Further, the halftone dots of each color have an arbitrary angle (this is called a screen angle) as shown in FIG. 6, and the distance between the centers of the halftone dots is arranged to be constant (hereinafter, "halftone dot generation interval"). Will be called). If a certain period and angle are given, halftone dots of each color interfere with each other and moire occurs.

FIG. 7 is a diagram showing that, for example, different angles are provided for each color plate of R4C with respect to the inclination angles of the inclination pattern 36 shown in FIG. As described above, if a certain period and angle are provided, halftone dots of each color interfere with each other and moire occurs. Therefore, in order to prevent the occurrence of moire, as shown in FIG. 7, It is desirable to provide different tilt angles for each color plate so that the halftone dots do not overlap.
For example, when Y (yellow) 40 is used as a reference (0 °), C41 may be 15 °, K42 may be 45 °, and M43 may be 75 °. Further, in Y (yellow) 40, the amount of movement of halftone dots may be set to 0, and the amount of movement of halftone dots of other colors may be set to other than 0. In this way, the angle formed by each color plate (from the reference) is an angle of 5 ° or more and less than 30 °.
By setting the angle of each color plate to a different value in this way, it is possible to prevent moire in areas other than the print area where moire is likely to occur. Further, by doing so, it is possible to limit the area where the halftone dots are moved in order to suppress moire. As a result, the print quality can be maintained and the efficiency of halftone dot image generation can be improved.

Further, as will be described later, the color plates for moving the halftone dots can be all color plates or some color plates. When the halftone dots are moved in all the color plates, the amount of movement of the halftone dots or the ratio of the moving halftone dots may be different for each color plate. At this time, cyan having a low spatial frequency sensitivity can have a larger amount of halftone dots moved, a ratio of moving halftone dots, or both of them, as compared with other color plates. Further, it may be handled in the same manner when the halftone dots are moved in some color plates. The color plate that does not move the halftone dots may be yellow, which has the lowest visibility.

Next, the printing method that is the premise of the present invention will be described with reference to FIGS. 8 to 12.

FIG. 8 is a schematic view of a printing machine 50 for printing a pattern on the printing surface of the printing body 52. The printing body 52 is supplied from the transport port 51, and inside each of the ink coating units 53 to 56, each ink set in the ink coating units 53 to 56 is transferred to the printing surface of the printing body 52. It is painted so that it is drawn according to the content you want to express by printing. In this way, the printed matter on which the content to be expressed by printing is drawn on the printed surface of the printed matter 52 by the ink coating unit is conveyed to the discharge port 57.

The printing speed of the printing machine 50 is preferably set to a value within the range of 200 m / min to 700 m / min. When printing at a higher speed, the transfer of ink may be affected by machine vibration or the like. In this case, the halftone dot reproducibility is deteriorated, and color shift and moire due to the printing machine may easily occur.

In the ink application units 53 to 56, different inks are set for each unit. The ink coating units 53 to 56 according to the embodiment of the present invention can be at least one unit, that is, at least one color, and it is particularly desirable that the ink coating units 53 to 56 have four colors of CMYK (this is referred to as R4C). Regarding the application of ink using these four colors as an example, the ink application unit 53 may be K, the ink application unit 54 may be C, the ink application unit 55 may be M, and the ink application unit 56 may be Y. When printing in this order, printing is performed from K, which is most likely to affect moiré, so that irregular moiré can be prevented from occurring.
If moire occurs irregularly, it may be difficult to identify the area where the halftone dots are moved. In other words, by printing from K, which tends to affect moiré, it becomes easier to identify the area where moiré occurs.

The inks set in the ink coating units 53 to 56 according to the embodiment of the present invention include, for example, general ink, process ink, gold ink, silver ink, carton ink, fluorescent ink, off-wheel ink, and ultraviolet curable type (UV). ) Ink, infrared dry type (IR) ink and the like are included. Further, this general ink may be produced as a series of 20 to 50 colors by an ink manufacturer.

Further, the ink set in the ink coating units 53 to 56 according to the embodiment of the present invention may be a composition. This composition may contain, for example, a colorant component, a vehicle (varnish) component, or the like as an essence. In addition, this composition may further contain an auxiliary component. Moreover, the colorant component may be either an organic pigment or an inorganic pigment. Further, the vehicle component may contain a resin or a solvent. The auxiliary agent component may be added to enhance the friction resistance of the ink, and may be, for example, a wax, a surfactant, a gelling agent, or the like.

In addition, the above-mentioned ink may have thick halftone dots due to the fluidity of the ink used during printing, but it is difficult to uniformly specify this fluidity according to the ink, so it is used in the printing process in commercial printing. Adjustment may be made each time based on the behavior of the printing ink. Further, in the halftone dot image, the halftone dots may be reduced by the thickness of the print. Since the thickness of the halftone dots varies depending on the amount of movement of the halftone dots, when the halftone dots are moved significantly, the adjustment amount of the size of the halftone dots is made larger than that of the non-moved portion. May be good.

The printing method in the present invention may be a plate type or a plateless type. However, as an embodiment of the present invention, it is particularly desirable to print by a plate type. The plate printing type here may include lithographic printing, letterpress printing, intaglio printing, stencil printing, and the like. Flat plate printing is often referred to as offset printing, letterpress printing as letterpress printing, concave printing as gravure printing, and stencil printing as screen printing. The moire suppressing means of the present invention may be applied to any printing method, but is particularly effective for lithographic printing.

The print body 52 is a print information paper. The print information paper here may be, for example, non-coated printing paper, finely coated printing paper, coated printing paper, special printing paper, or information paper. However, it is desirable that the printed matter 52 be either uncoated printing paper or coated printing paper.

The uncoated printing paper may include, for example, printing paper A, printing paper B, printing paper C, D, and the like. The printing paper A is a high-quality paper made by using 100% of bleached chemical pulp as a raw material. The printing paper B is a paper made by using 70% or more of bleached chemical pulp as a raw material, and is a medium-quality paper having a whiteness of 70%. The printing paper C is a paper made by using 40% or more and less than 70% of bleached chemical pulp as a raw material, and has a whiteness of about 65%. The printing paper D is a paper made by using less than 40% of bleached chemical pulp as a raw material, and has a whiteness of about 55%. The printing papers C and D are collectively low-grade paper.

Further, pulp is a fiber extracted from a raw material, and the main component is cellulose. The raw material may include, for example, wood, non-wood, recycled paper, synthetic fibers and the like. Wood pulp is made from softwood, hardwood, etc. Non-wood pulp is pulp made from plants, especially linter, kenaf, bagasse, bamboo and the like. Recycled paper pulp is made by deinking ink from paper and re-pulping it. Synthetic fiber pulp is made by pulping chemically synthesized fibers (rayon, vinylon, etc.). In addition, pulp includes mechanical pulp and chemical pulp. Mechanical pulp is pulp produced by mechanically grinding raw materials. Chemical pulp is pulp from which fibers are chemically extracted. The bleached pulp is bleached mechanical pulp or chemical pulp.

The coated printing paper may include, for example, art paper, coated paper, lightweight coated paper, finely coated paper, and the like. Art paper is high-quality paper or medium-quality paper coated with 40 g of a coating agent on both sides per square meter. The coated paper is a high-quality paper or a medium-quality paper coated with 20 g of a coating agent on both sides per square meter. Lightweight coated paper is high-quality or medium-quality paper coated with 15 g of a coating agent on both sides per square meter. The finely coated paper is a high-quality paper or a medium-quality paper coated with a coating agent of 12 g or less on both sides per square meter.

As for the printing paper, the halftone dots are more likely to be thickened on the non-coated printing paper than on the coated printing paper. Among the uncoated printing papers, the possibility of generating dot gain in the order of printing paper D, printing paper C, printing paper B, and printing paper A decreases. Among the coated printing papers, the possibility that the mesh dots become thicker in the order of finely coated paper, lightweight coated paper, coated paper, and art paper decreases.

Depending on the type of printing paper described above, the degree of ink absorption changes, and halftone dots tend to thicken. Therefore, the number of screen lines to be used is taken into consideration and set appropriately depending on the printing target in commercial printing. For example, in the case of printing on low-grade paper, the number of screen lines may be 10 lines or more and less than 110. Further, in the case of printing on medium quality paper, the number of screen lines may be 110 lines or more and less than 210 lines. Further, in the case of printing on high-quality paper, the number of screen lines may be 210 lines or more and less than 2000 lines. The ratio of moving halftone dots is considered to be set according to the number of screen lines.

That is, when the number of screen lines is 10 lines or more and less than 110, the ratio of moving halftone dots may be 35% or more and less than 70%. When the number of screen lines is 110 lines or more and less than 210 lines, the ratio of moving halftone dots may be 35% or more and less than 95%. When the number of screen lines is 210 lines or more, the range of the ratio of moving halftone dots may be determined by the following formulas 1 and 2.
[Number 1]
35 (number of screen lines-2000) / (210-2000) ≤ ratio of halftone dots

[Number 2]
Percentage of halftone dots <95 (screen lines-2000) / (210-2000)

In addition, when the number of screen lines is 10 lines or more and less than 210 lines, the ratio of moving halftone dots is 40% or more and 60% when both roughness and moire are appropriately suppressed (printed matter). It is desirable to be less than. Further, when giving priority to suppressing roughness (printed matter), it is desirable that the ratio of moving halftone dots is 35% or more and less than 40%. When priority is given to moire suppression, when the number of (printed matter) screen lines is 10 lines or more and less than 110, it is desirable that the ratio of moving halftone dots is 60% or more and less than 70%. When the number of screen lines is 110 lines or more and less than 210 lines, it is desirable that the ratio of moving halftone dots is 60% or more and less than 95%.
By setting the number of screen lines in such a range, it is possible to reduce the occurrence of print roughness due to excessive movement of halftone dots while sufficiently suppressing moire.

FIG. 9 is a schematic view of the inside of the ink coating units 53 to 56 of FIG. First, the dampening water roller 63 adheres the dampening water 64 to the printing plate 62 set in the plate cylinder 61. After that, the ink roller 65 adheres the ink 66 to the printing plate 62. Next, the ink 66 is transferred (off) from the printing plate 62 to which the ink 66 is attached to the rubber blanket 67. Further, the printing body 52 is pressed against the rubber blanket 67 on which the ink 66 is transferred by the impression cylinder 68, so that the ink 66 is transferred (set) to the printing body 52. As a result, the content to be expressed by printing is printed on the print body 52.

FIG. 10 is a diagram for explaining the printing plate 62. The print plate 62 may be, for example, a PS plate, a CTP plate, or a wipe-on plate, but the PS plate is particularly preferable. Further, the PS plate may be any of aluminum, stainless steel, and chromium, which are metals having strong hydrophilicity (the contact angle between the surface of the substance and water is close to 0 degrees), but aluminum is particularly preferable. .. Further, the printing plate 62 may have a metal surface coated with an ultraviolet curable resin. FIG. 10 shows the developed surface of the printing plate 62, and is composed of a lipophilic region 71 representing the drawing contents and a hydrophilic region 72 other than that.

FIG. 11 is a schematic view showing the flow up to the development of the printing plate 62. First, a plate-making film 76 composed of a region 74 representing the drawing content and a region 75 not representing the drawing content is placed on the printing plate 62 on which the ultraviolet curable resin 73 is coated on the surface, and is vacuum-tightened. After that, the surface of the printing plate is exposed to ultraviolet rays by the light source lamp 77, and alkali solubility is imparted to the photosensitive portion of the surface of the ultraviolet curable resin 73. The light source lamp 77 may be, for example, a mercury lamp. Further, when the photosensitive portion of the exposed PS plate is dissolved with a strong alkaline developer, the remaining region becomes a lipophilic region 71, and the dissolved region has a bare metal surface and is hydrophilic. It becomes the region 72 with. In this way, the printing plate 62 is made.

FIG. 12 is a schematic view until the dampening water 64 adheres to the printing plate 62. The dampening water roller 63 causes the dampening water 64 to adhere to the hydrophilic region 72 on the surface of the printing plate 62. At this time, the dampening water 64 does not adhere to the lipophilic region 71 due to its low affinity with water.

FIG. 13 is a schematic view until the ink 66 adheres to the printing plate 62. The ink roller 65 causes the ink 66 to adhere to the lipophilic region 71 on the surface of the printing plate 62. At this time, since the ink 66 is repelled by the dampening water 64 to the region 72 to which the dampening water 64 is attached, the ink 66 does not adhere.

The printing in the embodiment of the present invention has been described above. Hereinafter, the moire suppressing method according to the embodiment of the present invention will be described.

As described above, in the embodiment of the present application, in the input image represented by halftone dots, for the region where moire is generated (first region), each of them is based on a predetermined halftone dot generation interval. A grid that divides the halftone dots into individual cells is generated, and at least one of the halftone dots of the ratio determined based on the first arbitrary value (first pseudo-random number) among the halftone dots included in the grid. The movement direction and the third arbitrary value (third pseudo-random number) determined based on the second arbitrary value (second pseudo-random number) for the part (for example, a part of the pixels constituting the halftone dots). By moving according to the amount of movement determined based on the above, the period of halftone dots can be disrupted and the expression of moire can be suppressed.

Next, the movement of halftone dots according to the embodiment of the present invention will be described with reference to FIGS. 14 to 15.

FIG. 14 is a diagram showing a state before the halftone dots according to the embodiment of the present invention are moved. As shown in FIG. 14, the halftone dots 163 before movement are included in the cells 161 of the grid described above, and are composed of a plurality of dots (pixels) 162. The arrow 164 indicates the moving direction in which each dot 162 moves in the cell. The method of setting this moving direction will be described later.

FIG. 15 is a diagram showing a state after the halftone dots according to the embodiment of the present invention have been moved. As shown in FIG. 15, each dot 162 of the halftone dot before movement shown in FIG. 14 is moved according to the arrow 164 to become a deformed halftone dot 165 after movement.
The method of setting the movement amount for moving each dot 162 and the deformation due to the movement of the halftone dots will be described later.

By moving the halftone dots in this way, the period of the halftone dots can be disrupted and the expression of moire can be suppressed.
Although FIGS. 14 to 15 have described an example of the movement of halftone dots according to the embodiment of the present invention, the present invention is not limited thereto. For example, the movement of halftone dots according to the present invention shifts or flattens the center of gravity of halftone dots by moving the dots (pixels) constituting a specific ratio of halftone dots in the area where moire is generated. It means that the overlapping of halftone dots of each color plate is changed by moiré pattern of halftone dots, deformation, or other halftone dots.
Here, it is desirable that the ratio of halftone dots to be moved within the region is uniform. In this uniform state, the standard deviation of the percentage of dots (pixels) constituting the halftone dots to be moved within a 1 mm circle of 10 points in the region may be 10% or less.

Next, with reference to FIG. 16, the moire suppressing method according to the embodiment of the present invention will be described.

FIG. 16 is a diagram showing a moire suppressing method 800 according to an embodiment of the present invention. This moire suppressing method 800 may be carried out by, for example, each functional unit included in the moire suppressing device described with reference to FIG.

First, in step S801, it is determined whether or not moire has occurred in the target input image. Whether or not this moiré has occurred is determined by a method in which a human user projects an input image on a display or the like, prints the input image with an inkjet machine or the like, and then visually confirms the moiré. It may be performed by a means (neural network or the like) that automatically detects the presence or absence of moire based on the period, pitch, etc. of the pattern in the input image. However, in order to reduce the cost of printing, it is desirable to use a method for determining the occurrence of moire on the data.
If the occurrence of moire is determined, the present process proceeds to step S802, and if the occurrence of moire is not determined, the present process ends.

Further, the input image here is a halftone dot expressed by performing RIP processing on the submitted data by any one of the number of lines at the time of printing (about 60 lines or more). It is the data before making the printing plate, which has the design information.

In step S802, it is determined whether or not the print image data before halftone dot conversion can be used (whether it is at hand or received) for the input image in which moire is generated. If it is determined that the print image data before the halftone dot formation can be used, the present process proceeds to step S803, and if it is determined that the print image data cannot be used, the present process proceeds. Proceeds to S804.

Step S803 is a step performed when it is determined in step S802 that the print image data before halftone dot conversion can be used. In this step S803, a process of extracting the contour region of the object to be reflected in the image is performed on the print image data before halftone dot conversion. For the halftone dots included in the extracted contour area, the processing for halftone dots performed in the steps after this step is excluded.
This is because if the halftone dots included in the contour area are moved, noise may be generated and the contour of the object may be blurred.

FIG. 17 is a diagram showing a flow of processing for extracting a contour region in step S803. When the image data for printing before halftone dot conversion is input, first, a smoothing process for suppressing noise in the image is performed in advance. After that, a process of extracting the brightness change value is performed by a filter that quantifies the brightness change in the image. Then, by using a specific threshold value, a process of binarizing the brightness change value is performed. As a result, the extracted contour area can be output.

The smoothing process described above may be freely selected by the user, but it is particularly desirable to use a Gaussian filter. Further, the filter for quantifying the change in brightness may be freely selected by the user, but it is particularly desirable to use the sobel filter. In addition, contour extraction is not automatically processed, and it is possible to configure it so that it can be specified manually by the user.

Step S804 is a step performed when it is determined in step S802 that the print image data before halftone dot conversion cannot be used. In this step S804, a process of extracting the contour region of the object to be reflected in the image is performed on the print image data. For the halftone dots included in the extracted contour area, the processing for halftone dots performed in the steps after this step is excluded.
This is because if the halftone dots included in the contour area are moved, noise may be generated and the contour of the object may be blurred.

FIG. 18 is a diagram showing a flow of processing for extracting a contour region in step S804. When the print image data is input, first, a smoothing process for completely removing the halftone dot shape on the print image data is performed. After that, a process of extracting the brightness change value is performed by a filter that quantifies the brightness change in the image. Then, by using a specific threshold value, a process of binarizing the brightness change value is performed. As a result, the extracted contour area can be output.
The smoothing process described above may be freely selected by the user, but it is particularly desirable to use a Gaussian filter. Further, the filter for quantifying the change in brightness may be freely selected by the user, but it is particularly desirable to use the sobel filter. In addition, contour extraction is not automatically processed, and it is possible to configure it so that it can be specified manually by the user.

19 to 20 are diagrams showing specific examples in the case where contour extraction is performed by the procedure shown in FIGS. 17 to 18. FIG. 19 shows the print image data 1910 before halftone dot formation, which is the target of the process of step S803, and the print image data 1920, which is the target of the process of step S804. As shown in FIG. 19, the print image data 1910 before halftone dot formation is not represented by halftone dots, but is a normal image, and the print image data 1920 is represented by halftone dots. Has been done.

FIG. 20 shows an example of an image after the above-mentioned smoothing process is applied to each of the print image data 1910 before halftone dot formation and the print image data 1920 shown in FIG. It is a figure. As shown in FIG. 20, the smoothing process performed on the print image data 1920 (that is, the process performed in step S804) is performed on the print image data 1910 before halftone dot conversion. It is desirable that it is more powerful than the smoothing process performed on the surface. It is necessary to take care so that the shape of the halftone dots of the print image data 1920 does not remain, and smoothing for the purpose of simple noise suppression performed on the print image data 1910 before the halftone dots are formed. This is because it is naturally stronger than the conversion.

FIG. 21 is a diagram showing a result of extracting a contour region from the print image data 1910 and the print image data 1920 after the smoothing process and before the halftone dot formation, which is shown in FIG. Is. FIG. 21 shows an image 2110 obtained by extracting the contour area of the print image data 1910 before halftone dot conversion, and an image 2120 obtained by extracting the contour area of the print image data 1920.

FIG. 22 is a diagram showing an example of contour images 2210 and 2220 extracted by binarizing each of the image 2110 shown in FIG. 21 and the image 2120. Further, FIG. 23 is a diagram showing overlapping images 2310 in which the contour images 2210 and 2220 shown in FIG. 22 are superimposed and displayed.
As shown in FIG. 23, the contour area 2310 (core portion) output from the print image data before halftone dot formation and the contour area 2320 (core portion sandwiched) output from the print image data. Comparing with the portion), it can be seen that the contour region 2310 output from the print image data before halftone dot conversion is extracted with higher accuracy.

Returning to the process of FIG. 16, in step S805, plate making data including the region where moire is generated is selected. The plate-making data selected here is at least one or more plate-making data out of the four plate-making data for each print element color of the submitted data, and it is possible to narrow down the selection to one or two in particular. Is desirable. This is because when three or more plate-making data are selected and the halftone dots are moved, useless noise is generated. Further, the plate making data here is binary image data in which the design is represented by halftone dots by RIP processing.

Next, in step S806, for the plate making data selected in S805, a grid is generated in which halftone dots are divided into individual cells one by one. This grid is generated according to the distance between the centers of the halftone dots to be processed and the adjacent halftone dots (halftone dot generation interval) according to the halftone dot of the AM screen set in each version. Here, this grid is not a line drawn on the actual data, but an index generated to visualize the movement process.

An example of the grid is shown in FIG. As shown in FIG. 24, the grid 111 includes a plurality of cells 113. Further, it is desirable that the grid 111 is generated so that one halftone dot fits in each cell 113. Further, x114 shown in FIG. 24 is the spacing of the grid 111 in the horizontal direction, and similarly, y116 represents the spacing of the grid 111 in the vertical direction. The interval x114 of the grid 111 in the horizontal direction and the interval y116 of the grid 111 in the vertical direction are collectively referred to as "halftone dot generation interval".
In addition, x114 and y116 may have the same value. These halftone dot generation intervals are calculated by the calculation of the following mathematical formula 3.
[Number 3]
x = y = resolution of halftone dot image [dpi] / number of lines of halftone dot image [lpi]

Regarding the AM screen in the embodiment of the present invention, the number of screen lines can be in the range of 60 lines or more. The shape of the halftone dots may be selected from square, elliptical, round, chain, TH net and the like.

Next, in step S807, the cells in which the halftone dots to be moved are housed are uniformly determined in the grid of the entire plate making data. The number of cells (that is, halftone dots) determined here may be all cells included in the grid, but it is desirable to set the number to a specific ratio in order to reduce noise. More specifically, here, the number of cells to be moved is a halftone dot of a ratio determined based on a first arbitrary value (for example, a first pseudo-random number) among the cells of the grid. good. The range of this ratio may be, for example, 35% or more and 95% or less, and more preferably 40% or more and 60% or less. However, the range of this ratio may be set based on the conditions of the input image (halftone dot density, etc.).
Variations within ± 20% are allowed for this proportion bias. However, if the grid is determined beyond the range of proportions due to this bias, it is possible to readjust the cell determination so as not to exceed the range.

As described above, the moire suppression (that is, the movement process) is applied to the contour peripheral portion extracted by an arbitrary method and the covered region (for example, the contour region extracted in step S803 and step S804) among the cells. It is desirable not to apply. This is because if the halftone dots included in the contour area are moved, noise may be generated and the contour of the object may be blurred.
Further, the contour peripheral portion described above may be extracted by an arbitrary method and then subjected to a process of expanding the region. This is done for the purpose of preventing the deterioration of the entire output (that is, the object) by preventing the deterioration of the peripheral portion of the contour caused by the suppression process.

FIG. 12 is a diagram showing a range of ratios recommended for each resolution according to the printing paper to be used with respect to the range of ratios described above. The range of the ratio is a set value with the number of lines applied to medium-quality paper, mainly from 110 lines to 210 lines. On the other hand, regarding the number of lines applied to low-grade paper from 60 to 110 lines, the size of the halftone dots is larger than that of medium-quality paper, so the halftone dots are moved by nearly 95%. If this happens, it is clear that the roughness will be noticeable, and it is desirable to lower the upper limit of the moving ratio to some extent. Further, in the number of lines applied to high-quality paper of 210 lines or more, the size of the halftone dots is smaller than that of the medium-quality paper, and the visibility of moire with the naked eye is also low. It is desirable to set the ratio range lower as the number of lines increases.

In addition, this ratio was set because 35 types of verification samples were subjected to comparative verification under the light source of a fluorescent lamp for color evaluation for 10 subjects, and good results were obtained as a moire suppressing effect. It is a thing.

Pseudo-random numbers according to the embodiment of the present invention (for example, a first pseudo-random number for determining the movement ratio of the net points, a second pseudo-random number for determining the movement direction of the net points, and a movement amount of the net points). The third pseudo-random number for determining,) is the square congruential method, linear congruential method, linear feedback shift register, Mersenne Twister, Multiply with With Carry, Xorshift, Lugged Fibonacci method, RANLUX, Permuted congruential generator, Blum- It may be a value generated from any of Blum-Shub and Fortuna methods.

When the moire suppression process according to the embodiment of the present invention is implemented by a program, in order to control the arbitrary plate making data so as to obtain the same performance, the pseudo-random numbers generated by the above method are used. You can create and operate a random number table. This random number table enumerates a plurality of predetermined random number values. Therefore, the same suppression performance can be obtained by using the random number values extracted from the same random number table each time the processing of the embodiment of the present invention is performed. Further, the random number table may be created and operated with a capacity suitable for the specifications of the computer owned by each user for executing the process according to the embodiment of the present invention, for example.

Next, in step S808, the moving direction of each halftone dot of the cell determined in step S807 is determined. This moving direction may be determined based on, for example, a second arbitrary value. As a general rule, the moving direction here may be freely selected in any direction of 360 degrees for each halftone dot. However, depending on the processing performance of the computer that executes the program, it is desirable that the moving direction is an integral multiple of 360 / n ° (n ∈ N: n represents a natural number and N represents the entire natural number). As a result, the halftone dots can be moved evenly, and moire can be effectively suppressed.

It is particularly desirable that the number of candidates n in the moving direction is n = 2, 4, 6, 8, 12, 16, 18, 20, and 24. By using this number of candidates for the moving direction, it becomes easy to form a halftone dot image when the halftone dots are moved.

FIG. 26 is a diagram showing an example of determining the moving direction of dots (pixels) constituting the halftone dots included in the grid described above. In FIG. 26, the case where the number of movement direction candidates n = 4 described above is described as an example, but the present invention is not limited to this.

The moving direction of the halftone dots 112 is one of the four directions represented by at least 131 to 134, which is determined based on a pseudo-random number (for example, a second pseudo-random number). Further, with respect to θ1 to θ4 shown in FIG. 26, the angle between two adjacent directions can be 40 degrees or more and 140 degrees or less, and particularly preferably 45 degrees. The range of this angle varies depending on the number of candidates for the moving direction, but as shown in Equation 4, the angle between the directions is adjusted to the angle when the number of candidates is divided equally, thereby simplifying the program processing. It is possible to make it.

[Number 4]
Desirable angle θ = 360 / n

Further, the range of this angle is set in consideration of breaking the period of halftone dots as intended, and there may be a variation of about ± 10 degrees so as to fall within the range of the angle.

Next, in step S809, the halftone dots included in the cell determined in step S807 are moved based on the predetermined movement amount and the movement direction determined in step S808. The halftone dots moved here may be all of the halftone dots (that is, all the pixels that make up the halftone dots), or a part of the halftone dots (a part of the pixels that make up the halftone dots). May be good.
The predetermined movement amount here may be a preset value, or may be an amount determined from a predetermined range based on a pseudo-random number (for example, a third pseudo-random number). .. Further, this predetermined range may be, for example, a range based on the above-mentioned halftone dot generation interval.

27 to 28 are diagrams for explaining the movement of halftone dots included in the above-mentioned grid. FIG. 27 is a diagram showing an example of the halftone dot 112 movement process. The halftone dot movement amount r shown in FIG. 27 can be set to a size of 1/7 times or more and 1/3 times or less of the interval of the cells 113. As described above, the movement amount r of the halftone dots was determined based on a pseudo-random number (for example, a third pseudo-random number) from the range of 1/7 times or more and 1/3 times the interval of the cell 113. It may be the amount of movement.
The range of the halftone dot movement amount r was set because 35 types of verification samples were comparatively verified under the light source of a fluorescent lamp for color evaluation for 10 subjects, and good results were obtained. It is a thing.
As shown in FIG. 27, the halftone dot 112 before movement becomes the halftone dot 141 after movement by moving each of the included pixels according to the halftone dot movement amount r.

Further, the halftone dot movement amount r may be a value selected from a range of 1/7 times or more and 1/3 times or less of the grid spacing, depending on the density value expressed for each halftone dot. For example, it is possible to change the halftone dot movement amount r depending on the texture such as the pitch of the shading of the pattern represented by the halftone dots. Further, the amount of movement of the halftone dots can be determined by a function that monotonically increases as the pitch of shading increases. As an example, the above-mentioned movement amount can be determined as follows.

When the pattern represented by the halftone dots has a fine-grained structure that is almost invisible to the naked eye, such as a silk fabric, the halftone dot movement amount is a small value within the above-mentioned movement amount range. , A sufficient moire suppressing effect can be obtained. At this time, the example of the pitch of the shade may be, for example, 100 μm or more and less than 300 μm. The pitch of this shade can be calculated from the component that becomes the peak of the spatial frequency by obtaining the distribution of the spatial frequency by image processing of the printed matter. The amount of movement in such a case may be 1/7 times or more and less than 1/5 of the grid spacing.
Further, when the pattern represented by the halftone dots has a coarse structure that can be visually recognized by the naked eye, such as a sweater woven with yarn, the halftone dot movement amount is within the range of the above-mentioned movement amount. Of these, by setting a large value, a moire suppressing effect can be obtained. At this time, the example of the shade pitch may be, for example, 1 mm or more and less than 3 mm. The amount of movement in such a case may be 1/4 times or more and 1/3 or less of the cell spacing.
Further, when the pattern represented by the halftone dots has a structure such as a pattern on a shirt that is visible or invisible to the naked eye, the halftone dot movement amount is within the range of the above-mentioned movement amount. By setting the value to an intermediate value, a moire suppressing effect can be obtained. At this time, an example of the shade pitch may be, for example, 300 μm or more and less than 3 mm. The amount of movement in such a case may be 1/5 times or more and 1/4 or less of the cell spacing.

FIG. 28 is an explanatory diagram in which the amount of movement of halftone dots is decomposed in the horizontal and vertical directions. When the halftone dots are moved in the pixel space, the halftone dots are moved by calculating the horizontal movement amount x'and the vertical movement amount y'from the values of the movement amount r shown in FIG. 27. The coordinates can be calculated. The decomposition movement amount can be calculated by the following formulas 5 and 6, respectively.
[Number 5]
x'= r x cos θ'
[Number 6]
y'= r x sin θ'

When the calculated x'and y'are decimal points in the above formulas 5 to 6, the decimal number is within a range not exceeding 1/7 times or more and 1/3 times or less of the cell spacing. The first decimal place may be replaced with a rounded integer value.

The above-mentioned movement amount is the same movement amount regardless of the shade of the region where moire is generated. Further, regarding the shading here, assuming that the value of each of the four colors of R4C is expressed by a decimal number from 0 to 100, any two colors or less having a value of 40 or less among the three colors of C, M, and Y. The color obtained by mixing K with 20 or less is a light color.

Next, in step S810, it is determined whether or not exception processing is executed when a part of the halftone dots (that is, one pixel or more) exceeds the cell boundary as a result of the halftone dot movement processing performed in step S809. Will be done. If it is determined that it is necessary to execute this exception processing, this processing proceeds to step S811, and if it is determined that it is not necessary to execute the exception processing, this processing proceeds to step S812. ..

In step S811, as a result of the halftone dot movement processing performed in step S809, exception processing is performed when a part of the halftone dots (that is, one pixel or more) exceeds the cell boundary line. An example of this exception handling is shown in FIG.

The first state 2910 shown in FIG. 29 shows the state of the cell 113 before moving the halftone dots 112. The second state 2920 shown in FIG. 29 shows the state of the cell 113 and its peripheral region immediately after moving the halftone dot 112. Further, the third state 2930 shown in FIG. 29 shows the state of the halftone dots 112 remaining inside the cell 113 after the movement.

The region surrounded by the dotted line shown in the third state 2930 represents a part of the pixels of the halftone dots 112 beyond the boundary line of the cell 113, and is a region to be cut from the halftone dots 112. The gray area shown in the third state 2930 represents a pixel area adjacent to the element 151 of the halftone dots 112 remaining inside the cell 113, and the halftone dots 112 beyond the boundary line of the cell 113. It is a candidate pixel area for rearranging by the number of pixels of. Of this candidate area, the pixel area to be rearranged is determined by a pseudo-random number.

Further, the fourth state 2940 shown in FIG. 29 shows the state of the cell 113 after the rearrangement of the pixels. Regarding the halftone dots 152 after the rearrangement, the pixel area A154 represents the rearranged pixel area.

The above-mentioned exception handling moves if the halftone dots 112 are moved beyond the boundary line of the cell 113, considering that the halftone dots 112 are configured based on the number of pixels required to express the color in the cell 113. It is necessary to do this because the color may change before and after the treatment.

Next, in step S812, it is determined whether or not the halftone dot movement processing is completed for all the cells determined in step S807. When the process is completed, the plate making data after the moire suppression process is output. If the processing is not completed, the processing after step S808 is performed on the unprocessed cell 113.

By moving only the halftone dots in the area where moiré is generated based on the pseudo-random number by the moiré suppression method described above, the moiré is effectively suppressed, the noise is suppressed, and the structure of the object is maintained more clearly. Image can be obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

31 Gradation pattern 32, 33, 34 Enlarged area 51 Transport port 52 Print body 53, 54, 55, 56 Ink coating unit 57 Discharge port 61 Plate cylinder 62 Printing plate 63 Damping water roller 64 Damping water 65 Ink roller 66 Ink 67 Rubber blanket 68 Impressor 71 Area with lipophilicity on which the design is expressed 72 Area with hydrophilicity other than the design 73 Ultraviolet curable resin 74 Design area on the plate-making film 75 Area other than the design on the plate-making film 76 Plate-making film 77 Light source lamp 111 Grid 112 Halftone dot 113 Cell 131, 132, 133, 134 Movement direction 141 Halftone dot 151 after halftone dot movement Halftone dot element 152 Reconstructed after exception processing Point 161 Cell where halftone dots are arranged 162 Pixels that make up halftone dots 163 Halftone dots 164 Direction of movement of dots that make up halftone dots 165 Halftone dots that make up halftone dots 360 after movement of dots Moare suppression system 365 Client terminal 370 Communication network 372 Data storage 374 Halftone dot generation condition input unit 375 Printing unit 380 Halftone suppression processing unit 382 Halftone dot area extraction unit 384 Halftone dot movement condition determination unit 386 Halftone dot movement processing unit 388 Exception processing Part 390 Image output part S801-S812 Flowout item of printing moire suppression method

Claims (10)

In the input image represented by halftone dots, the process of generating a grid that divides each halftone dot into individual cells for the first region where moire occurs, and
Of the halftone dots included in the grid, at least a part of the halftone dots of the ratio determined based on the first arbitrary value, the moving direction determined based on the second arbitrary value, and the third The process of moving according to the movement amount determined based on an arbitrary value, and
Including
At least one of the first arbitrary value, the second arbitrary value, and the third arbitrary value is a pseudo-random number.
A moire suppression method characterized by this. In the input image represented by halftone dots, a step of generating a grid that divides each halftone dot in the second region where moire is generated, and
Of the halftone dots included in the grid, at least a part of the halftone dots of the ratio determined based on the fourth arbitrary value is the moving direction determined based on the fifth arbitrary value and the sixth. The process of moving according to the movement amount determined based on an arbitrary value, and
Including
At least one of the fourth arbitrary value, the fifth arbitrary value, and the sixth arbitrary value is a pseudo-random number.
The moire suppression method according to claim 1, wherein the moire is suppressed. The moire suppression method according to claim 1, wherein the first arbitrary value is a pseudo-random number selected from the range of 40% to 60%. The moving direction is one direction selected from at least four directions based on the second arbitrary value.
The moire suppressing method according to claim 1, wherein the angle between two adjacent directions among the four directions is 40 degrees to 140 degrees. The moire suppression method according to claim 1, wherein the third arbitrary value is a pseudo-random number selected from a range of 1/7 to 1/3 of a predetermined halftone dot generation interval. When at least a part of the halftone dots crosses the cell boundary as a result of moving a specific halftone dot, the pixels of the halftone dots that cross the boundary line are crossed the boundary line of the halftone dots. The moire suppressing method according to claim 1, further comprising a step of rearranging the dots in an adjacent region adjacent to a part thereof. The input image is
At least one selected from four-color plate making data for color printing.
The moire suppression method according to claim 1, wherein the moire is suppressed. Moire suppression device
In the input image represented by halftone dots, a halftone dot area extraction unit that generates a grid that divides each halftone dot into individual cells for the first region where moire occurs,
Regarding the halftone dots included in the grid, the ratio of the halftone dots to be moved is determined based on the first arbitrary value, the movement direction is determined based on the second arbitrary value, and the movement amount is determined by the third arbitrary value. Halftone dot movement condition determination unit that determines based on an arbitrary value of
Of the halftone dots included in the grid, at least a part of the determined halftone dots of the ratio is moved according to the determined movement direction and the determined movement amount to generate a final image in which the moire is suppressed. Halftone dot movement processing unit and
An image output unit that outputs the final image and
Including
At least one of the first arbitrary value, the second arbitrary value, and the third arbitrary value is a pseudo-random number.
A moire suppression device characterized by this. When at least a part of the halftone dots crosses the cell boundary as a result of moving a specific halftone dot, the pixels of the halftone dots that cross the boundary line are crossed the boundary line of the halftone dots. The moire suppression device according to claim 8, further comprising an exception handling unit that is rearranged in an adjacent area adjacent to a part of the moire pattern. Moire suppression system
In the moire suppression system
The client terminal, the printing unit, and the moire suppression device are connected via a communication network.
The moire suppression device is
When an input image represented by halftone dots is received
In the input image, for the first region where moire is generated, a grid that divides each halftone point into individual cells is generated.
Regarding the halftone dots included in the grid, the ratio of the halftone dots to be moved is determined based on the first arbitrary value, the movement direction is determined based on the second arbitrary value, and the movement amount is determined by the third arbitrary value. Determined based on any value of
Of the halftone dots included in the grid, at least a part of the determined halftone dots of the ratio is moved according to the determined movement direction and the determined movement amount to generate a final image in which the moire is suppressed. ,
The final image is output to the printing unit or the client terminal, and the final image is output to the printing unit or the client terminal.
At least one of the first arbitrary value, the second arbitrary value, and the third arbitrary value is a pseudo-random number.
A moiré suppression system characterized by this.

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